CA1260815A

CA1260815A - Flexible mandrel

Info

Publication number: CA1260815A
Application number: CA000523655A
Authority: CA
Inventors: Rick A. Anderson
Original assignee: Goodyear Tire and Rubber Co
Current assignee: Goodyear Tire and Rubber Co
Priority date: 1985-11-25
Filing date: 1986-11-24
Publication date: 1989-09-26
Also published as: US4738816A; MX165858B; BR8605682A

Abstract

Abstract of the Disclosure FLEXIBLE MANDREL
There is disclosed a flexible mandrel for making tubular products comprising an elastomeric portion surrounding a reinforcing cable comprised of wire cables twisted around a non-metallic core. There is also disclosed a process for making a flexible mandrel and a process of making a hose using the flexible mandrel.

Description

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FLEXIBLE MANDREL

Field This invention relates to a flexible mandrel used for making indefinite lengths of tubular products.
More particularly it relates to a reinforced flexible mandrel for making hoses.

Back~round Art Flexible mandrels have been in existence for many years. Ini~ially they were solid cylindrical extrusions of rubber or plastic upon which the various layers of polymers and reinforcement were built to form tubular products. These suffered from lack of dimensional s1.ability in both the radial and the longitudinal directions as well as the inability to repair or connect broken sections. The next modification was to introduce a reinforcing cable about which the rubber or plastic cylinder was extruded to form a mandrel. While this provided dimensional stability and repairability, the service life was shortened as a result o~ using water pressure to blow the flexible mandrel out of the tubular product. It is believed that the water entered the core of the cable reinforcement thereby attacking the wire and destroving the rubber or plastic to wire adhesion which in turn caused a loss of dimensional stability.
In order to overcome this wicking action of water entering through the core of a wire cable, the next modification was to use a non-metallic cable made of a somewhat compressible thermoplastic material, e.g., a polyamide. This solid or tightly stranded material when used as the core for the extruded rubber or plastic cylinder provided dimensional stability and '_, 94 ., , :
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Summary of the Invention An aspect of the invention is as follows:
A process for making a hose comprised of the steps of:
(a) providing a flexible mandrel having an elastomeric portion surrounding a reinforcing cable comprised of wire cables twisted around a non-metallic core and (b) building the hose around the flexible mandrel of step (a).

Brief Description of the Drawinqs Figure 1 is a side sectional view of the flexible mandrel of this invention.

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Figure 2 is a cross-section of Figure 1 taken along line 2-2.
Figure 3 represents a cross-sectional view of the prior art solid elastomeric mandrel.
Figure 4 is a cross-sectional view of a prior art wire cable reinforced mandrel.
Figure 5 is a cross-sectional view of a prior art non-metallic reinforced mandrel.

Detailed Description of the Drawin~s Figure 1 and Figure 2 i.llustrate the non-metallic core l, which can be solid or stranded, about which has been twisted wire cables 2 to form the reinforcing member over which is extruded the elastomeric portion 3 to form the flexible mandrel of this invention.
Figure 3 illustrates the prior art unreinforced flexible mandrel having only the elastomeric portion 3.
Figure 4 shows a prior art wire cable reinforcement

2 surrounded by an elastomeric portion 3.- The incompressible strands or cables are so constructed or configured as to leave an open space between adjacent strands or cables.
Fi~,ure 5 shows a prior art mandrel with an elastomeric portion 3 reinforced with a non-metallic material 1 which is compressible enough to eliminate the spaces between adjacent strands, Detailed Description of the Invention The flexible mandrel of this invention comprises a cylindrical elastomeric portion which is applied around a reinforcing cable which comprises wire cables twisted around a non-metallic core. The elastomeric portion can be any one of a number of compounded elastomers suitable for the purpose of making flexible mandrels.

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s term elastomer generally connotes a thermosetting polymer, it is meant to include any polymer which exhibits flexibility ln the temperature range of building and curing operations oE the tubular products thereon and is capable of maintaininF, its shape.
The reinforcing cable can be made by twisting individual wire strands into individual cables which are then twisted themselves around the non-metallic core. The non-metallic core can be individual strands or filaments which are twisted together tightly in order to eliminate any spaces between the individual strands or it can be a solid core. The non-metallic core material tnust be somewhat compressible, i.e., it must be compressible enough to conform itself within the internal portion of the wire cable and to its own twistings, if stranded, so as to elimi~ate any void spaces. The non-metallic material must be such as to not be deformed or decomposed within the temperature range of the tubular product building and curing operations. The preferred non-metallic material is an aromatic polyamide The flexible mandrels of this invention can be made in flny size within the limitations of being capable o~
fittin~, the reinforcing portion within the elastomeric portion while having the tensile strength requlred to withstand handling in a particular tubular product building proces~. Generally the size can range from 6mm to about 40mm, however, larger sizes would only be limited by the size of the equipment available to handle the mandrels and/or the tubular products made with the mandrels.

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Three strands of 1500 denier aroma~ic polyamide fiber were twisted together to form a core for a reinforcement cable. The core was then wrapped with six steel wire cables in a twisted fashion having a lay of 15mm in an S direction. Each steel wire cable contained six 0.2mm strands having a lay around one 0.2mm strand of about 4mm in the Z direction. This reinforcement core was then passed through an extruder and covered with an RPDM rubber compound to orm a flexible mandrel having an outside diameter of 8mm.
The flexible mandrel was cut into individual mandrels of about 200m in length and used for making hoses wherein after the hose was built it was coiled on a drum and placed in an autoclave for curing. After curing and cooling, water pressure was applied to one end of the hose to blow out the mandrel.
Whereas the prior experience with flexible mandrels reinforced only with wire cable provided a serviceable life of 7 to 10 cycles, the flexible mandrels of the present invention have surpassed 30 to 40 cycles.
While cert:ain representatlve embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modificati.ons may be made therein without departing from the spirit or scope of the invention.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for making a hose comprised of the steps of:
(a) providing a flexible mandrel having an elastomeric portion surrounding a reinforcing cable comprised of wire cables twisted around a non-metallic core and (b) building the hose around the flexible mandrel of step (a).